Objective: The major goal of the total project involves the study of a number of cytoplasmic biochemical properties of nervous system tumors which show promise as discriminating factors between tumor and normal tissue and which may be employed to enhance specificity of therapeutic agents. Of particular interest is the further investigation of the nature of increased acid hydrolase activities found by us in human and experimental tumors and the possibility of differing responses to lysosomal labilizers in tumors compared to normal brain. The other systems to be investigated include: quantitative activity of the hexosemonophosphate pathway, measurement of exchangeable blood flow in growth zones of tumor and of adjacent brain, measurement of intracellular pH in tumor of growth zones, quantitation of rates of extra-cellular protein incorporation into glioma cells, and the rates of penetration of large molecules into the various growth zones of tumors. These studies are planned primarily for use in nitrosourea induced tumors in rats. Approach: The effect of Vitamin A preparation and x-irradiation upon the cerebral implantation model will be studied in additional cell lines representing mixed gliomas and in cloned cell lines derived from astrocytomas. Measurement of rates of hydrolase activities upon substrates presented in vivo will be carried out. Collaboration has been initiated with members of Experimental Pharmacology for trial for a series of compounds requiring initial activation of hydrolytic enzymes. Acidic and basic iso-enzymes of five acid hydrolases will be separated by gel electrophoresis on lysosome rich preparations of tumor and kinetics of hydrolases studied with isoelectric focusing techniques. The study of the hexosemonophosphate pathway will begin with the use of glucose-1-C14 and glucose-6-C14 substrates on tumor slices for determination of C1 and C6 ratios after short incubation intervals.